中文摘要：

以贝加尔针茅草原为目标,研究不同程度的放牧干扰对草地土壤微生物数量、土壤酶活性、土壤养分和土壤呼吸的影响及其相互关系,旨在为贝加尔针茅草原生态系统的保护、恢复及重建提供科学依据。结果表明：随着放牧强度的增加,土壤微生物总数量显著降低（P〈0.05）;各放牧区土壤微生物数量均表现为：细菌〉固氮菌〉放线菌〉真菌;垂直分布为0~10 cm〉10~20 cm;随着放牧强度的增加,土壤脲酶、过氧化氢酶、转化酶、磷酸酶均显著降低（P〈0.05）;0~10 cm土层的土壤酶活性均高于10~20 cm;土壤养分含量、土壤含水量随着放牧强度的增加亦显著降低（P〈0.05）;土壤pH、土壤容重则逐渐增加,在不同放牧压力处理条件下差异显著（P〈0.05）。相关分析表明,土壤酶活性与土壤微生物数量、土壤养分含量密切相关,放牧干扰条件下土壤中真菌数量与脲酶活性呈显著正相关（P〈0.05）,固氮菌数量与脲酶活性达到极显著正相关（P〈0.01）,转化酶和磷酸酶与土壤全磷含量呈显著正相关（P〈0.05）。

英文摘要：

In order to provide scientific basis for protection,restoration and reconstruction of Stipa baicalensis Rosev.steppe ecosystem,the effect of different grazing disturbance levels on the soil microorganisms,soil enzyme activities,soil nutrients,and soil respiration of S.baicalensis steppe was studied and the interrelationship among them was analyzed.The results show that the total number of soil microorganisms reduced significantly（P0.05） along with the increasing of grazing intensity,the number of microorganisms in different grazing areas showed the same changing trends： bacterianitrogen germactinomycetesfungi;higher in soil depth 0~10 cm than 10~20 cm in the vertical distribution.The activities of soil urease,catalase,invertase,and phosphatase reduced significantly（P0.05） with the increasing of grazing intensity and showed similar vertical distribution as microorganisms did.The soil nutrients and soil moisture also reduced significantly（P0.05） when the grazing intensity increased.However soil pH and bulk density increased gradually and showed significant difference（P0.05） under different grazing pressures.Correlation analysis indicates that the soil enzyme activities were positively related to soil microorganisms and soil nutrients.Fungal quantity had a high-positive correlation with urease activity（P0.05）,the number of nitrogen germ was extreme-significantly correlated with urease activity（P0.01） and soil total phosphorus was high-positively correlated with invertase and phosphatase（P0.05）.